1. Field of the Invention
The disclosures herein relate to a touch panel.
2. Description of the Related Art
A touch panel (i.e., touchscreen panel) is an input device that allows input to be directly entered into a display, and is generally placed in front of the display. Touch panels are widely used in various applications because of their capability of allowing direct input based on visual information provided by the display.
A resistive-type touch panel is widely known in the art. The resistive-type touch panel includes an upper electrode substrate and a lower electrode substrate having respective transparent conductive films. These substrates are arranged such that the corresponding transparent conductive films face each other. When pressure is applied to a point on the upper electrode substrate, the transparent conductive films are brought into contact with each other, thereby allowing the position of the pressed point to be detected.
The resistive-type touch panel is classified into a four-wire type, a five-wire type, and a diode type. In the four-wire type, an X-axis electrode is disposed on one of the upper electrode substrate and the lower electrode substrate, and a Y-axis electrode is disposed on the other substrate (see Patent Document 1, for example). In the five-wire type, an X-axis electrode and a Y-axis electrode are both disposed on the lower electrode substrate while the upper electrode substrate serves as a probe for detecting voltage (see Patent Document 2, for example).
A touch panel as described above is operated by a finger or the like coming into contact with the touch panel. The finger that is used to operate the touch panel may also come in contact with various other objects. Upon touching an object with static charge, the finger may be charged with static electricity. Operating a touch panel with the finger charged with static electricity results in the static charge of the finger flowing into the touch panel, thereby destroying a semiconductor device such as an integrated circuit chip used in the touch panel. As a result, the touch panel may be broken.
As a preventive measure, an anti-electrostatic sheet may be attached to the surface of a touch panel. Alternatively, the finger may be brought into contact with a highly conductive object prior to operating a touch panel, which serves to remove static charge from the finger. Then, the touch panel may be operated by the use of the finger.
The measures described above are associated with problems. For example, a complex process may become necessary to manufacture the touch panel, resulting in a cost increase. It may otherwise be burdensome to operate a touch panel, and, also, a mistake made with respect to the order of operations may cause the destruction of the touch panel. Further, these measures may not be sufficient as an anti-electrostatic measure.
Accordingly, there may be a need for a touch panel provided with a sufficient anti-electrostatic measure, which neither causes a cost increase nor requires cumbersome operating steps.
[Patent Document 1] Japanese Patent Application Publication No. 2004-272722
[Patent Document 2] Japanese Patent Application Publication No. 2008-293129
[Patent Document 3] Japanese Patent Application Publication No. 2010-218542
[Patent Document 4] Japanese Patent Application Publication No. 2012-208750